/**
* Cipher API multi-part AEAD demonstration.
*
* This program AEAD-encrypts a message, using the algorithm and key size
* specified on the command line, using the multi-part API.
*
* It comes with a companion program psa/aead_demo.c, which does the same
* operations with the PSA Crypto API. The goal is that comparing the two
* programs will help people migrating to the PSA Crypto API.
*
* When used with multi-part AEAD operations, the `mbedtls_cipher_context`
* serves a triple purpose (1) hold the key, (2) store the algorithm when no
* operation is active, and (3) save progress information for the current
* operation. With PSA those roles are held by disinct objects: (1) a
* psa_key_id_t to hold the key, a (2) psa_algorithm_t to represent the
* algorithm, and (3) a psa_operation_t for multi-part progress.
*
* On the other hand, with PSA, the algorithms encodes the desired tag length;
* with Cipher the desired tag length needs to be tracked separately.
*
* This program and its companion psa/aead_demo.c illustrate this by doing the
* same sequence of multi-part AEAD computation with both APIs; looking at the
* two side by side should make the differences and similarities clear.
*/
/*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
*/
/* First include Mbed TLS headers to get the Mbed TLS configuration and
* platform definitions that we'll use in this program. Also include
* standard C headers for functions we'll use here. */
#include "mbedtls/build_info.h"
#include "mbedtls/cipher.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
/* If the build options we need are not enabled, compile a placeholder. */
#if !defined(MBEDTLS_CIPHER_C) || \
!defined(MBEDTLS_AES_C) || !defined(MBEDTLS_GCM_C) || \
!defined(MBEDTLS_CHACHAPOLY_C)
int main(void)
{
printf("MBEDTLS_MD_C and/or "
"MBEDTLS_AES_C and/or MBEDTLS_GCM_C and/or "
"MBEDTLS_CHACHAPOLY_C not defined\r\n");
return 0;
}
#else
/* The real program starts here. */
const char usage[] =
"Usage: cipher_aead_demo [aes128-gcm|aes256-gcm|aes128-gcm_8|chachapoly]";
/* Dummy data for encryption: IV/nonce, additional data, 2-part message */
const unsigned char iv1[12] = { 0x00 };
const unsigned char add_data1[] = { 0x01, 0x02 };
const unsigned char msg1_part1[] = { 0x03, 0x04 };
const unsigned char msg1_part2[] = { 0x05, 0x06, 0x07 };
/* Dummy data (2nd message) */
const unsigned char iv2[12] = { 0x10 };
const unsigned char add_data2[] = { 0x11, 0x12 };
const unsigned char msg2_part1[] = { 0x13, 0x14 };
const unsigned char msg2_part2[] = { 0x15, 0x16, 0x17 };
/* Maximum total size of the messages */
#define MSG1_SIZE (sizeof(msg1_part1) + sizeof(msg1_part2))
#define MSG2_SIZE (sizeof(msg2_part1) + sizeof(msg2_part2))
#define MSG_MAX_SIZE (MSG1_SIZE > MSG2_SIZE ? MSG1_SIZE : MSG2_SIZE)
/* Dummy key material - never do this in production!
* 32-byte is enough to all the key size supported by this program. */
const unsigned char key_bytes[32] = { 0x2a };
/* Print the contents of a buffer in hex */
static void print_buf(const char *title, unsigned char *buf, size_t len)
{
printf("%s:", title);
for (size_t i = 0; i < len; i++) {
printf(" %02x", buf[i]);
}
printf("\n");
}
/* Run an Mbed TLS function and bail out if it fails.
* A string description of the error code can be recovered with:
* programs/util/strerror <value> */
#define CHK(expr) \
do \
{ \
ret = (expr); \
if (ret != 0) \
{ \
printf("Error %d at line %d: %s\n", \
ret, \
__LINE__, \
#expr); \
goto exit; \
} \
} while (0)
/*
* Prepare encryption material:
* - interpret command-line argument
* - set up key
* - outputs: context and tag length, which together hold all the information
*/
static int aead_prepare(const char *info,
mbedtls_cipher_context_t *ctx,
size_t *tag_len)
{
int ret;
/* Convert arg to type + tag_len */
mbedtls_cipher_type_t type;
if (strcmp(info, "aes128-gcm") == 0) {
type = MBEDTLS_CIPHER_AES_128_GCM;
*tag_len = 16;
} else if (strcmp(info, "aes256-gcm") == 0) {
type = MBEDTLS_CIPHER_AES_256_GCM;
*tag_len = 16;
} else if (strcmp(info, "aes128-gcm_8") == 0) {
type = MBEDTLS_CIPHER_AES_128_GCM;
*tag_len = 8;
} else if (strcmp(info, "chachapoly") == 0) {
type = MBEDTLS_CIPHER_CHACHA20_POLY1305;
*tag_len = 16;
} else {
puts(usage);
return MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA;
}
/* Prepare context for the given type */
CHK(mbedtls_cipher_setup(ctx,
mbedtls_cipher_info_from_type(type)));
/* Import key */
int key_len = mbedtls_cipher_get_key_bitlen(ctx);
CHK(mbedtls_cipher_setkey(ctx, key_bytes, key_len, MBEDTLS_ENCRYPT));
exit:
return ret;
}
/*
* Print out some information.
*
* All of this information was present in the command line argument, but his
* function demonstrates how each piece can be recovered from (ctx, tag_len).
*/
static void aead_info(const mbedtls_cipher_context_t *ctx, size_t tag_len)
{
mbedtls_cipher_type_t type = mbedtls_cipher_get_type(ctx);
const mbedtls_cipher_info_t *info = mbedtls_cipher_info_from_type(type);
const char *ciph = mbedtls_cipher_info_get_name(info);
int key_bits = mbedtls_cipher_get_key_bitlen(ctx);
mbedtls_cipher_mode_t mode = mbedtls_cipher_get_cipher_mode(ctx);
const char *mode_str = mode == MBEDTLS_MODE_GCM ? "GCM"
: mode == MBEDTLS_MODE_CHACHAPOLY ? "ChachaPoly"
: "???";
printf("%s, %d, %s, %u\n",
ciph, key_bits, mode_str, (unsigned) tag_len);
}
/*
* Encrypt a 2-part message.
*/
static int aead_encrypt(mbedtls_cipher_context_t *ctx, size_t tag_len,
const unsigned char *iv, size_t iv_len,
const unsigned char *ad, size_t ad_len,
const unsigned char *part1, size_t part1_len,
const unsigned char *part2, size_t part2_len)
{
int ret;
size_t olen;
#define MAX_TAG_LENGTH 16
unsigned char out[MSG_MAX_SIZE + MAX_TAG_LENGTH];
unsigned char *p = out;
CHK(mbedtls_cipher_set_iv(ctx, iv, iv_len));
CHK(mbedtls_cipher_reset(ctx));
CHK(mbedtls_cipher_update_ad(ctx, ad, ad_len));
CHK(mbedtls_cipher_update(ctx, part1, part1_len, p, &olen));
p += olen;
CHK(mbedtls_cipher_update(ctx, part2, part2_len, p, &olen));
p += olen;
CHK(mbedtls_cipher_finish(ctx, p, &olen));
p += olen;
CHK(mbedtls_cipher_write_tag(ctx, p, tag_len));
p += tag_len;
olen = p - out;
print_buf("out", out, olen);
exit:
return ret;
}
/*
* AEAD demo: set up key/alg, print out info, encrypt messages.
*/
static int aead_demo(const char *info)
{
int ret = 0;
mbedtls_cipher_context_t ctx;
size_t tag_len;
mbedtls_cipher_init(&ctx);
CHK(aead_prepare(info, &ctx, &tag_len));
aead_info(&ctx, tag_len);
CHK(aead_encrypt(&ctx, tag_len,
iv1, sizeof(iv1), add_data1, sizeof(add_data1),
msg1_part1, sizeof(msg1_part1),
msg1_part2, sizeof(msg1_part2)));
CHK(aead_encrypt(&ctx, tag_len,
iv2, sizeof(iv2), add_data2, sizeof(add_data2),
msg2_part1, sizeof(msg2_part1),
msg2_part2, sizeof(msg2_part2)));
exit:
mbedtls_cipher_free(&ctx);
return ret;
}
/*
* Main function
*/
int main(int argc, char **argv)
{
/* Check usage */
if (argc != 2) {
puts(usage);
return 1;
}
int ret;
/* Run the demo */
CHK(aead_demo(argv[1]));
exit:
return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
}
#endif